Method of forming a semiconductor device including a pitch multiplication

ABSTRACT

Disclosed herein is a manufacturing method of a semiconductor device that includes forming first and second layers over an underlying martial such that the first layer is between the underlying material and the second layer, forming a third layer over the second layer, forming first and second core portions apart from each other over the third layer, forming a gap portion between the first and the second core portions; and removing the second and the third layers by using the first and the second core portions and the gap portion as a mask to expose a part of the first layer.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S. patentapplication Ser. No. 14/810,711, filed Jul. 28, 2015, entitled “MethodOf Forming A Semiconductor Device Including A Pitch Multiplication”,naming Lionel LUPO as inventor, which claims benefit to foreign Japaneseapplication JP 2014-156666, filed on Jul. 31, 2014, entitled “Method OfForming A Semiconductor Device Including A Pitch Multiplication”, namingLionel LUPO as inventor, the disclosures of which are incorporated byreference.

TECHNICAL FIELD

The present invention relates generally to methods of forming asemiconductor device, in particular, to a method including process stepsto form smaller features of below a resolution limit of the exposuretool.

BACKGROUND OF THE INVENTION

A photolithography technique is known as a technique according to whicha material formed on a substrate is etched using a photoresist patternobtained by photomask-utilized light-exposure and development of aphotoresist, as a mask. In a quest for improved resolution, a thinnerphotoresist becomes necessary, which has led to a situation where thethinner photoresist alone cannot offer sufficient etching resistance. Todeal with this problem, a technique has come into wide use, according towhich a photoresist pattern is transferred to a mask material, such assilicon nitride film that can be processed by the thinner photoresist,and then a work piece formed on a substrate is etched, using thissilicon nitride film as a mask, to form a pattern. Such a siliconnitride film is referred to as hard mask.

A demand for microfabrication and high densification of semiconductormemories, etc., has been so intensified in recent years that the pace ofan improvement in resolution through development of lithographictechniques including exposure systems and photoresist materials is notfast enough to meet such a demand. Under these circumstances, techniquesby which patterns are formed at a pitch smaller than a lithographyresolution limit, utilizing a hard mask, has become widely noticed.

According to one of such techniques, a core pattern is formed first, anda spacer is formed on the side walls of the core pattern, and then ahard mask material is buried in recessions between different parts ofthe spacer to form a gap pattern. Subsequently, the spacer is eliminatedselectively to form a pattern between the core pattern and the gappattern, the formed pattern being identical in width with the spacer,thus having a pitch smaller than the lithography resolution limit. Thistechnique is referred to as SADP (Self-Aligned Double Patterning).

An LELE (Litho-Etch-Litho-Etch) technique is known as a method offorming active areas of island patterns surrounded by isolation regionsformed by an STI (Shallow Trench Isolation) method. According to theLELE method, a desired pattern is formed by combining a first patterncreated by the first round of lithography and etching with a secondpattern created by the second round of lithography and etching. Theabove SADP technique is adopted to form the first pattern, whose pitchis thus reduced to half by the SADP technique, and a part of the firstpattern is cut by the second pattern. Through this process, fine islandpatterns having a pitch smaller than the resolution limit can be formed.

Japanese Patent Application Laid Open No. 2008-103718, Japanese PatentApplication Laid Open No. 2011-233878.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a structure of DRAM which is a suitablesemiconductor device to implement a manufacturing method in accordancewith an embodiment of the present invention.

FIG. 2 (a) is a cross-sectional view of the semiconductor device along aline A-A′ or a line B-B′ in FIG. 1, (c) is a cross-sectional view of thesemiconductor device along a line C-C′ in FIG. 1.

FIG. 3 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 4 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 3, respectively.

FIG. 5 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 6 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 5, respectively.

FIG. 7 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 8 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 7, respectively.

FIG. 9 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 10 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 9, respectively.

FIG. 11 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 12 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 11, respectively.

FIG. 13 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 14 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 13, respectively.

FIG. 15 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 16 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 15, respectively.

FIG. 17 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 18 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 17, respectively.

FIG. 19 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 20 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 19, respectively.

FIG. 21 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 22 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 21, respectively.

FIG. 23 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 24 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 23, respectively.

FIG. 25 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 26 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 25, respectively.

FIG. 27 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 28 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 27, respectively.

FIG. 29 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 30 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 29, respectively.

FIG. 31 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 32 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 31, respectively.

FIG. 33 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 34 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 33, respectively.

FIG. 35 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 36 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 35, respectively.

FIG. 37 is a plan view of a manufacturing method in accordance with anembodiment of the present invention.

FIGS. 38 (a), (b), (c) are cross-sectional views of a manufacturingmethod in accordance with an embodiment along the line A-A′, B-B′, C-C′in FIG. 37, respectively.

FIGS. 39 and 40 are plan views of a manufacturing method in accordancewith another embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail with reference to the accompanying drawings. In the accompanyingdrawings, various components used for detailed description of thepresent invention are depicted in their arbitrarily enlarged or reducedforms, which do not imply the actual or relative size of the depictedcomponents.

A DRAM (Dynamic Random Access Memory), which is a semiconductor devicemanufactured preferably by a manufacturing method for a semiconductordevice of the present invention, will first be described briefly.

FIG. 1 is a schematic plan view of a structure of a semiconductor deviceaccording to a preferred embodiment of the present invention. FIG. 2(a)is a cross-sectional view of the semiconductor device along a line A-A′or a line B-B′ in FIG. 1, and FIG. 2(c) is a cross-sectional view of thesemiconductor device along a line C-C′ in FIG. 1.

As shown in FIGS. 1, 2 (a), and 2(c), a semiconductor device 1 accordingto this embodiment serves as a DRAM and includes a semiconductorsubstrate 100. This semiconductor substrate 100 is, for example, asilicon substrate. On the main surface of the semiconductor substrate100, a field oxide film 108 making up isolation regions formed by theSTI (Shallow Trench Isolation) method is buried. In a memory cell arrayarea, multiple active areas 105 surrounded by the field oxide film 108are formed.

Each of the multiple active areas 105 is of a parallelogram having twopairs of opposed sides one of which pairs extend in the Y directionwhile the other of which pairs extend in an X′ direction inclinedagainst the X and Y directions. The active areas 105 are arranged inrepetition in the X and Y directions into a matrix formation. In eachactive area 105, two memory cells are formed. In the active area 105located at an end of the memory cell array area, however, only onememory cell may be formed. As a width between the pair of opposed sidesextending in the X′ direction gets smaller and smaller to approach theresolution limit of an exposure system, the apexes of the parallelogrammay become degenerated round shapes or the linear portions of the pairof opposed sides extending in the X′ direction may become too obscure tovisually recognize.

In the memory cell array area, multiple word lines (gate electrodes) 114and multiple bit lines 127 are formed.

The word lines 114 are conductive patterns buried in gate trenchesformed on the main surface of the semiconductor substrate 100. Betweeneach conductive pattern and the inner surface of each gate trench, agate dielectric film 111 is formed. The word line 114 is buried in thelower part of the gate trench, while a silicon nitride film 117 (capdielectric film) covering the upper surface of the word line 114 isburied in the upper part of the gate trench. The silicon nitride film117 is sandwiched between a storage node contact plug 140, which will bedescribed later, the bit line 127, and the word line 114. The word lines114 are extended linearly in the Y direction such that two word lines114 pass through one active area 105. However, as shown in FIG. 1, onlyone word line 114 may pass through each active area 105 located at anend of the memory cell array area.

The bit lines 127 are made of conductive patterns formed above the mainsurface of the semiconductor substrate 100. Each bit line 127 meandersand passes through the centers of the active areas 105 arranged in the Xdirection, thus by and large extending in the X direction in terms of anoverall view. According to this embodiment, the bit line 127 is amultilayer film composed of a poly-silicon film 124, a titanium nitridefilm 125, and a tungsten film 126. The upper surface of the bit line 127is covered with a hard mask film (cover dielectric film) 128, whoseupper surface is exposed from the upper surface of an interlayerdielectric film 122.

The hard mask film 128 is disposed between a cell capacitor 158 and thebit line 127. Each bit line 127 has its side faces covered with siliconnitride films (side face dielectric films) 130 each serving as adielectric film. Each of these silicon nitride films (side facedielectric films) 130 is sandwiched between the storage node contactplug 140, which will be described later, and the bit line 127.

The internal structure of the active area 105 will be described. Ap-well (not depicted) is formed in a region in the interior ofsemiconductor substrate 100 that is close to its surface, the interiorof semiconductor substrate 100 being equivalent to the interior ofactive area 105. Inside the p-well, in a region close to the surface ofthe semiconductor substrate 100, diffusion layers 120 a and 120 b areformed by diffusing an n-type impurity into the region. Both of thesediffusion layers 120 a and 120 b are formed by implanting impurity ionsinto the semiconductor substrate 100. As shown in FIG. 1, the diffusionlayers 120 a and 120 b in the active area 105 are divided into threeportions by two word lines 114 corresponding to the active area 105.Among the three portions, the diffusion layer 120 a located at thecenter of the active area 105, that is, located between two word lines114 serves as a source/drain region common to two cell transistors(access transistors) making up two memory cells included in the activearea 105, and is connected to the bit line 127 corresponding to thediffusion layer 120 a, via a bit line contact plug 132. The diffusionlayers 120 b and 120 b, i.e., the other two portions, make up anothersource/drain region of the above two cell transistors, and are connectedto lower electrodes 150 of the cell capacitors 158 corresponding to thediffusion layers 120 b and 120 b, via the storage node contact plugs140.

An interlayer dielectric film 135 is formed on the main surface of thesemiconductor device 100, and the bit line 127 is formed in thisinterlayer dielectric film 135. The position of the upper surface of theinterlayer dielectric film 135 is adjusted so that the upper surface ofthe interlayer dielectric film 135 becomes flushed with the upperssurface of the hard mask film 128 covering the upper surface of the bitline 127.

The cell capacitors 158 are each composed of the lower electrode 150, acapacitance dielectric film 152, and an upper electrode 156.

The lower electrode 150 is a bottomed cylindrical conductor making upeach cell capacitor 158. The lower electrode 150 is constructed byforming a cylindrical hole penetrating a dielectric film or siliconnitride film temporarily formed during the manufacturing process andthen covering the inner surface of the cylindrical hole with theconductor.

As shown in FIG. 1, each lower electrode 150 is so located that itoverlaps the corresponding storage node contact plug 140 in a plan view,and has its lower surface in contact with the storage node contact plug140, as shown in FIGS. 2(a) and 2(b). The storage node contact plug 140is so formed as to penetrate the interlayer dielectric film 122, and hasa lower surface in contact with the corresponding diffusion layer 120 band an upper surface in contact with the lower electrode 150 of thecorresponding cell capacitor 158.

On a part of the upper end of the lower electrode 150, as shown in FIG.2(a), a support film 154 made of, for example, silicon nitride isformed, which support film 154 connects the lower electrode 150 to adifferent lower electrode 150.

The capacitance dielectric film 152 is a thin dielectric film coveringthe whole of the surface, which includes the inner and outer surfaces,of the bottomed cylindrical lower electrode 150. The upper electrode 156is a conductor formed such that it is counter to the lower electrode 150across the capacitance dielectric film 152. In other words, the cellcapacitor 158 has a structure in which the lower electrode 150 and theupper electrode 156 are counter to each other across the capacitancedielectric film 152. As shown in FIGS. 2(a) and 2(b), the upper surfaceof the upper electrode 156 is covered with a silicon oxide film 160. Theupper electrode 156 is connected to an upper line 164 via a contact plug162 penetrating the silicon oxide film 160.

A method of manufacturing the semiconductor dice 1 will then bedescribed.

FIGS. 3 to 38 are diagrams for explaining a method of manufacturing thesemiconductor device according to a first embodiment of the presentinvention. Of these diagrams, diagrams denoted by odd figure numbers(FIG. 3, etc.) are plan views and diagrams denoted by even figurenumbers (FIG. 4, etc.) are cross-sectional views. Diagrams denoted byeven figure numbers with (a) appended thereto are cross-sectional viewstaken along the line A-A′ in FIG. 1, the same with (b) appended theretoare cross-sectional views taken along the line B-B′ in FIG. 1, and thesame with (c) appended thereto are cross-sectional views taken along theline C-C′ in FIG. 1.

As shown in FIGS. 3, 4(a), 4(b), and 4(c), a pad dielectric film 200, afield nitride film 205, a carbon film 210, a first mask material layer215, a second mask material layer 220, and a third mask material layer225 are formed in increasing order on the semiconductor substrate 100,and then a three-layer resist is formed on the third mask material layer225 by depositing a first organic film 230, a first silicon-containingfilm 235, and a first photoresist 240 in increasing order on the thirdmask material layer 225.

The pad dielectric film 200 and field nitride film 205 are patternedinto the same shape as the shape of isolation trenches 103 in thesemiconductor substrate 100 (see FIG. 36), and serve as stopper layersthat are used when the field oxide film 108 (see FIGS. 2 and 38) is soformed as to fill up the isolation trenches 103 and the residual oxidefilm left on the part other than the isolation trenches is eliminated byCMP (Chemical/Mechanical Polishing) or anisotropic etching. The fieldnitride film 205 has a thickness that is needed to allow the fieldnitride film 205 to work effectively as the stopper layer against CMP oretching.

The carbon film 210 is a hard mask that is used when the field nitridefilm 205, pad dielectric film 200, and semiconductor substrate 100 areetched for patterning. The carbon film 210, therefore, must have athickness that allows the carbon film 210 to at least withstand etchingof the field nitride film 205.

The first mask material layer 215 is a hard mask material used forpatterning the carbon film 210. For the first mask material layer 215,an etching condition that realizes a desired selective etching ratio ofetching on the carbon film 210 must be set. It is preferable, if notabsolutely necessary, that the first mask material layer 215 be asilicon nitride film (SiN) or silicon oxynitride film (SiON).

The second mask material layer 220 is a layer that is used forsynthesizing line-and-space patterns (first and second mask patterns) inthe X′ direction formed by the first round of lithography and etchingand space patterns or hole patterns (third mask patterns) in the Ydirection formed by the second round of lithography and etching. For thesecond mask material layer 220, an etching condition that realizes adesired selective etching ratio of etching on the first mask materiallayer 215 and third mask material layer 225 must be set. It ispreferable that the second mask material layer 220 be, for example, asilicon oxide film (SiO).

The third mask material layer 225 is a hard mask that is used forpatterning the second mask material layer 220, and serves as an etchingstopper when a spacer material 245, which will be described later, isetched. For the third mask material layer 225, therefore, an etchingcondition that realizes a desired selective etching ratio of etching onthe second mask material layer 220 and spacer material 245 must be set.The third mask material layer 225 is, for example, a silicon nitridefilm (SiN) or silicon oxynitride film (SiON), and the spacer material245 should preferably be a silicon oxide film. The third mask materiallayer 225 may be thinner than that of the first mask material layer 215.

The first organic film 230 should preferably be sufficiently thickerthan a minimum interval to be formed and provide an almost flat surfacewhen filling up recessions of a substrate. The first silicon-containingfilm 235 should preferably have etching resistance higher than that ofthe first photoresist 240, and may be an organic film containing siliconof about 40 wt. % or SOD (Spin on Dielectric) film. The first organicfilm 230 and first silicon-containing film 235 should preferably beformed by spin coating.

The first photoresist 240 has etching resistance sufficient forpatterning the first silicon-containing film 235 and first organic film230. Like the above first organic film 230, the first photoresist 240can be formed by, for example, spin coating of an ArF photoresist.

Subsequently, as shown in FIGS. 5 and 6(a), 6(b), and 6(c), the firstphotoresist 240 is processed to form a first resist pattern 240 aserving as core portions. The first resist pattern 240 a is formed bypatterning using an ArF immersion exposure system. The first resistpattern 240 a is a pattern formed by arranging linear openings extendingin the X′ direction, repetitively at given intervals in the Y direction.It is preferable that a space between lines of the resist pattern 24that are adjacent to each other be 2 or 3 times as large in width aseach line of the resist pattern.

Subsequently, as shown in FIGS. 7, 8(a), 8(b), and 8(c), the firstsilicon-containing film 235 and first organic film 230 areanisotropically etched, using the first resist pattern 240 a as anetching mask, to transfer the first resist pattern 240 a to the firstsilicon-containing film 235 and first organic film 230, thereby form thecore portions (first mask pattern core portions 235/230) each composedof the first silicon-containing film 235 and first organic film 230. Asa result of this anisotropic etching, openings 230 a penetrating thefirst silicon-containing film 235 and first organic film 230 are formedunder the openings of the first resist pattern 240 a, where the surfaceof the third mask material layer 225 is exposed in the openings 230 a.

Subsequently, as shown in FIGS. 9 and 10(a), 10(b), and 10(c), asacrifice film, e.g., a space material 245 covering the side faces ofthe first silicon-containing film 235 and first organic film 230penetrated by the openings 230 a, is formed uniformly. The spacermaterial 245 may be formed such that its thickness on the side faces ofthe first organic film 230 is determined to be smaller than thelithography resolution limit. Formation of the spacer material 245 isperformed under a temperature lower than the heat resistance temperatureof the first organic film 230 and first silicon-containing film 235 andis so performed as to offer superior step coverage covering steps formedby the openings 230 a. Specifically, the spacer material 245 is formedunder a temperature equal to or lower than 200° C. or, preferably, equalto or lower than 50° C. The sacrifice film should preferably be made ofsilicon oxide. However, not only the silicon oxide but also a materialwhich can be formed under a temperature equal to or lower than 200° C.,offers fine step coverage for the side faces of the core portions, andallows adoption of a selective etching ratio of etching on an organicfilm is applicable as the sacrifice film.

The spacer material 245 is given a thickness with which the spacermaterial 245 does not fill up each opening 230 a completely. Forexample, when the arrangement pitch of the core portions is 100 nm andthe width W1 of each core portion is 25 nm, the thickness T1 of thespacer material 245 formed on the side faces of the opening 230 a isdetermined to be 25 nm that is equal to the width W1. As a result, arecession 245 a of spacer material 245 that has a width W3 of 25 nm isformed in each opening 230 a. In this case, the width W1 of the coreportion composed of the first organic film 230 and firstsilicon-containing film 235, the width W2 of the side wall spacer madeof the spacer material 245, and the width W3 of the recession 245 a ofthe spacer material 245 are all equal to each other. However, it is notnecessary to make all the widths W1, W2, and W3 equal to each other. Forexample, the width W1 is determined to be 30 nm and the thickness T1 isdetermined to be 20 nm to form the spacer material 245 with the widthsW1 and W3 each determined to be 30 nm and the width W2 determined to be20 nm.

Subsequently, as shown in FIGS. 11, 12(a), 12(b), and 12(c), a secondorganic film 250 is formed on the spacer material 245 to fill therecessions 245 a of the spacer material 245 with the second organic film250. It is preferable that the second organic film 250 have a thicknesswith which the second organic film 250 fills up the recessions 245 a andyet has an almost flat surface. In other words, the material that fillsup the recessions 245 a is not selected from limited types of materialsbut may be selected from any types of materials that have desiredrecession-filling properties and flatness and are formed under atemperature lower than the heat resistance temperature of the firstorganic film 230 and first silicon-containing film 235. For example,such a material may be selected from a photoresist, SOD (Spin onDielectric) film, etc.

Subsequently, as shown in FIGS. 13, 14(a), 14(b), and 14(c), the secondorganic film 250 on the spacer material 245 is eliminated by anisotropicetching to expose the top surface of the spacer material 245 whileleaving part of the second organic film 250 in the recessions 245 a ofthe spacer material 245. As a result, a gap portion bury mask (secondmask pattern) composed of the second organic film 250 buried in therecessions 245 a is formed. The width of the bury mask composed of thesecond organic film 250 is equal to the width of the recession 245 a.

Subsequently, as shown in FIGS. 15, 16(a), 16(b), and 16(c), the wallspacer made of the spacer material 245 is eliminated selectively byanisotropic etching. This etching is performed under a condition thatallows adoption of a selective etching ratio of etching on the secondorganic film 250, first silicon-containing film 235, and first organicfilm 230 and is carried out to selectively eliminate the side wallspacer only. This etching exposes the upper surface and both side facesof the core portions each composed of the first silicon-containing film235 and first organic film 230 and forms gap portions each of which is alamination of the second organic film 250 and the spacer material 245.The upper surface of the third mask material layer 225 is also exposedin areas between the core portions and the gap portions, in which areasthe side wall spacer has been placed until the etching.

According to this embodiment, the condition for anisotropic etching ofthe side wall spacer composed of the spacer material 245 is set as adesired selective etching ratio for the third mask material layer 225.This allows protection of the structure under the second mask materiallayer 220.

Subsequently, as shown in FIGS. 17, 18(a), 18(b), and 18(c), the thirdmask material layer 225 and the second mask material layer 220 areselectively eliminated by anisotropic etching using the second organicfilm 250, first silicon-containing film 235, and first organic film 230as an etching mask. By this etching, a line-and-space pattern consistingof alternating lines of core portions along two-dot broken lines A-A′shown in FIG. 17 (FIG. 18(a)) and gap portions along two-dot brokenlines B-B′ shown in FIG. 17 (FIG. 18(b)) is transferred to the secondmask material layer 220.

Subsequently, as shown in FIGS. 19, 20(a), 20(b), and 20(c), the secondorganic film 250, first silicon-containing film 235, and first organicfilm 230 are eliminated by plasma ashing. During the plasma ashing, thecarbon film 210 covered with the first mask material layer 215 isprotected from the ashing process and is therefore kept intact. Thespacer material 245 is also left as it is.

Subsequently, as shown in FIGS. 21, 22(a), 22(b), and 22(c), the spacermaterial 245 is eliminated by anisotropic etching. In this etchingprocess, if the exposed first mask material layer 215 is made of amaterial for which a desired selective etching ratio of etching on thespacer material 245 can be set, e.g., made of a silicon nitride film asthe third mask material layer 225 is, the spacer material 245 remainingon the gap portions can be eliminated selectively without etching thethird mask material layer 225 and first mask material layer 215. As aresult, the core portions and the gap portions are formed into uniformstructure each of which is a lamination of the third mask material layer225 and the second mask material layer 220 and has the same maskthickness.

Following this, the second round of lithography and etching starts. Inthe second round of lithography and etching, as shown in FIGS. 23,24(a), 24(b), and 24(c), a third organic film 232, a secondsilicon-containing film 237, and a second resist 242 are formed first inincreasing order.

Subsequently, as shown in FIGS. 25, 26(a), 26(b), and 26(c), the secondresist 242 is processed into a second resist pattern 242 a, which isformed by, for example, patterning using an ArF immersion exposuresystem. The second resist pattern 242 a includes patterns of linearopenings extending in the Y direction and repeated in the X direction atgiven intervals. At the core portions (FIG. 26(a)) and the gap portions(FIG. 26(b)), the structure below the third mask material layer 225 isthe same and therefore the same optical constant is obtained. As aresult, in principle, optical deviation caused by intervals between thesecond resist patterns 242 a on the core portions and the same on thegap portions can be avoided.

Subsequently, as shown in FIGS. 27, 28(a), 28(b), and 28(c), the secondsilicon-containing film 237 and third organic film 232 are etchedanisotropically, using the second resist pattern 242 a as an etchingmask, to transfer the second resist pattern 242 a to the secondsilicon-containing film 237 and third organic film 232. This etching isperformed under a condition that allows adoption of a selective etchingratio for the third mask material layer 225, and creates openings 232 apenetrating the second silicon-containing film 237 and third organicfilm 232. In the openings 232 a, respective surfaces of the third maskmaterial layer 225 and first mask material layer 215 having beenconcealed under the third organic film 232 until the etching areexposed.

Subsequently, as shown in FIGS. 29, 30(a), 30(b), and 30(c), the thirdmask material layer 225 and second mask material layer 220 areeliminated selectively by anisotropic etching using a pattern (thirdmask pattern) composed of the second silicon-containing film 237 and thethird organic film 232 as an etching mask. This etching transfers thesecond resist pattern 242 a to the third mask material layer 225 andsecond mask material layer 220. As a result, the space portions ofline-and-space patterns in the X′ direction and the space portions ofline-and-space patterns in the Y direction are synthesized to formmultiple island patterns.

Because the openings 232 a include the exposed part of the first maskmaterial layer 215, both first mask material layer 215 and third maskmaterial layer 225 must be made of the same material, such as siliconnitride, and the first mask material layer 215 must be made thicker thanthe third mask material layer 225 so that the first mask material layer215 remains as it is even when the third mask material layer 225 isetched.

Subsequently, as shown in FIGS. 31, 32(a), 32(b), and 32(c), the secondsilicon-containing film 237 and third organic film 232 are eliminated byplasma ashing. During this plasma ashing, the carbon film 210 coveredwith the first mask material layer 215 is protected from the ashingprocess and therefore remains as it is.

Subsequently, as shown in FIGS. 33, 34(a), 34(b), and 34(c), the firstmask material layer 215 and the carbon film 210 are eliminated byanisotropic etching, using the second mask material layer 220 as anetching mask. By this etching, the third mask material layer 225 is alsoeliminated. As a result, the island patterns are transferred to thecarbon film 210.

Subsequently, as shown in FIGS. 35, 36(a), 36(b), and 36(c), the fieldnitride film 205 and the pad dielectric film 200 are eliminatedselectively by anisotropic etching, using the carbon film 210 as anetching mask, and then the semiconductor substrate 100 is eliminatedselectively by anisotropic etching to form the isolation trenches 103.

Subsequently, as shown in FIGS. 37, 38(a), 38(b), and 38(c), theisolation trenches 103 are filled with the field oxide film 108 to forma pattern of field oxide film 108. Following this, other constituentelements are formed by a known method to complete the semiconductordevice 1 of FIGS. 1 and 2.

FIGS. 39 and 40 are diagrams for explaining a manufacturing method for asemiconductor device according to a different (another) embodiment ofthe present invention. Processes indicated in FIGS. 39 and 40 correspondto processes indicated in FIGS. 25 and 27 according to the abovepreferred embodiment, a cross-sectional view of FIG. 39 corresponds tothe cross-sectional view of FIG. 26, and a cross-sectional view of FIG.40 corresponds to the cross-sectional view of FIG. 28.

Processes indicated in FIGS. 3 to 24 of the different embodiment are thesame as the processes indicated in FIGS. 3 to 24 of the preferredembodiment. Following these processes, to form a second pattern, thesecond photoresist 242 is processed into the second resist pattern 242a. As shown in FIGS. 39 and 26, the second resist pattern 242 a isformed by arranging patterns of openings each consisting of multipleholes lined up cyclically in the Y direction, at given intervals in theX direction. In other words, the openings of the second resist pattern242 a of the different embodiment are not continuous line patterns butare broken line patterns extending intermittently in the Y direction.The holes may be formed into an elliptic or rectangular shape.

Subsequently, as shown in FIGS. 40 and 28, the second silicon-containingfilm 237 and third organic film 232 are etched, using the second resistpattern 242 a as a mask, to transfer the layout pattern of the secondresist pattern 242 a to the second silicon-containing film 237 and thirdorganic film 232. By this etching, openings penetrating the secondsilicon-containing film 237 and third organic film 232 are formed underthe openings of the second resist pattern 242 a. As a result, in theseopenings, the surface of the third mask material layer 225 or surface ofthe first mask material layer 215 is exposed. Processes to follow thisprocess are the same as the processes according to the preferredembodiment.

According to the different embodiment, the third mask material layer 225is formed on the second mask material layer 220, as is in the preferredembodiment. In the same manner as in the preferred embodiment of thepresent invention, therefore, portions along two-dot broken lines A-A′and portions along two-dot broken lines B-B′ shown in FIG. 40 are formedinto uniform structures each of which is a lamination of the third maskmaterial layer 225 and the second mask material layer 220 and has thesame mask thickness.

Preferred embodiments of the present invention have been describedabove. The present invention is not limited to the above embodiment butmay be modified into various forms of applications on the condition thatthe modification does not deviate from the substance of the presentinvention. Obviously, the modified forms of applications are alsoincluded in the scope of the invention.

For example, according to the above embodiments, the present inventionis applied as a processing method for forming the isolation regions thatdefine the multiple active areas on the semiconductor substrate. Thepresent invention, however, is applied not only to the formation ofisolation regions but also to various processes.

CONCLUSION

The disclosure provides a manufacturing method of a semiconductor devicethat includes forming first and second layers over an underlying martialsuch that the first layer is between the underlying material and thesecond layer, forming a third layer over the second layer, forming firstand second core portions apart from each other over the third layer,forming a gap portion between the first and the second core portions;and removing the second and the third layers by using the first and thesecond core portions and the gap portion as a mask to expose a part ofthe first layer.

The disclosure further provides a manufacturing method of asemiconductor device that includes forming first and second layers overan underlying martial such that the first layer is between theunderlying material and the second layer, forming a third layer over thesecond layer, forming first and second features respective includingside surfaces facing each other over the third layer, forming asacrifice film that covers the respective side surfaces of the first andthe second features so as to form a concave portion therebetween overthe third layer, forming a third feature in the concave portion of thesacrifice film, removing the sacrifice film between the third featureand each of the first and the second features to expose the third layer;and removing the second and the third layers in a region of the exposedpart of the third layer to expose a first part of the first layer.

The disclosure still further provides a manufacturing method of asemiconductor device that includes forming first and second layers overan underlying martial such that the first layer is between theunderlying material and the second layer, forming a third layer over thesecond layer, coating a first triple-layer including a first organicmaterial over the third layer, forming first and second features eachincluding the organic material by patterning the first triple-layer toexpose a part of the third layer, forming a spacer covering the exposedpart of the third layer and respective sidewall portions of the firstand the second features so as to form a concave portion between thefirst and the second features, coating a second organic material on thespacer, removing a part of the second organic material so as to remainthe second organic material in the concave portion of the spacer as athird feature, removing selectively each sidewall portion of the spacerbetween the third feature and each of the first and the second featuresto expose a first part of the third layer, removing the second and thethird layers in the first part of the third layer to expose a part ofthe first layer, removing the first and the second features to expose asecond part of the third layer and the third feature to expose aresidual spacer, removing the residual spacer, coating a secondtriple-layer, forming a fourth feature including an opening intersectingthe second part of the third layer and the exposed part of the firstlayer by patterning the second triple-layer, removing selectively thesecond and the third layers in the opening of the fourth feature toexpose another part of the first layer, removing the fourth feature,removing the exposed part of the first layer and the another exposedpart of the first layer with a residual third layer; and etching theunderlying material by using the second layers as a mask.

What is claimed is:
 1. A method comprising: forming a hard-mask layerover a semiconductor substrate; patterning the hard-mask layer to form apatterned hard-mask; and selectively removing the semiconductorsubstrate by using the patterned hard-mask as an etching mask; whereinthe patterning the hard-mask layer comprises: forming a first layer overthe hard-mask layer; forming a second layer over the first layer;forming a third layer over the second layer; forming a plurality ofpatterns over the third layer apart from each other; transferring theplurality of patterns to the third and second layers so that the thirdlayer is converted into a patterned third layer and the second layer isconverted into a patterned second layer; further converting thepatterned second layer into a further patterned second layer so that thefurther patterned second layer is different in pattern from thepatterned second layer; and transferring the further patterned secondlayer to the first layer and the hard-mask layer to form the patternedhard-mask.
 2. The method of claim 1, wherein the hard-mask layercomprises carbon.
 3. The method of claim 1, further comprising, beforeforming the hard-mask layer, forming a pad dielectric film over thesubstrate.
 4. The method of claim 3, further comprising, before formingthe hard-mask layer, forming a field dielectric film over the paddielectric material.
 5. The method of claim 1, wherein the furtherconverting the patterned second layer into the further patterned secondlayer comprises: covering the patterned second layer with a fourthlayer; patterning the fourth layer to from a patterned fourth layer; andtransferring the patterned fourth layer to the patterned second layer toform the further patterned second layer.
 6. The method of claim 5,wherein the patterned second layer is covered with the fourth layerwhile the patterned third layer is intervening between the patternedsecond layer and the fourth layer so that the patterned fourth layer isfurther transferred to the patterned third layer.
 7. The method of claim1, wherein the forming the plurality of patterns comprises: formingfirst and second core portions; and forming a gap portion between thefirst and second core portions.
 8. The method of claim 7, wherein theforming the gap portion comprises: forming a sacrificial layer over thefirst and second core portions to form a concave portion between thefirst and second core portions; filling the concave portion withdielectric material; and removing respective portions of the sacrificiallayer between the first core portion and the dielectric material andbetween the second core portion and the dielectric material to exposecorresponding portions of the third layer.
 9. The method of claim 1,wherein the selectively removing the semiconductor substrate causes toform a plurality of trenches into the semiconductor substrate.
 10. Themethod of claim 9, further comprising filling the plurality of trancheswith dielectric material to form a plurality of active regions definedby the plurality of tranches.
 11. The method of claim 10, furthercomprising: forming a plurality of buried word lines into thesemiconductor substrate, each of the plurality of buried word linescrossing associated one or ones of the plurality of active regions; andforming a plurality of access transistors into the plurality of activeregions, respectively, each of the access transistors comprising a firstdiffusion region, a second diffusion region and a channel region alongan associated one of the buried word lines between the first and seconddiffusion regions.
 12. The method of claim 11, further comprisingforming a plurality of capacitors each in electrical contact with thefirst diffusion region of an associated one of the plurality of accesstransistors.
 13. A structure made by the method of claim 1.